Touch screens are prevalent today, and generally include a transparent base substrate such as glass or polyethylene terephthalate (PET), and a transparent conductor pattern such as Indium Tin Oxide (ITO) on the base substrate. A conductive metal pattern such as copper and silver can be formed on the edges of the ITO pattern to provide a more conductive bus bar to reduce the resistivity in the touch screen.
Conductive metal patterns are typically provided with a conductive adhesive used to adhere the conductive metal pattern to the ITO pattern. In this case, resistivity can increase over time, and the conductive adhesive may fail at high temperature and humidity. Other conventional methods such as applying a silver frit are costly and may require a costly indium-based solder to be used for the attachment of wires. Electro-deposition of conductive metals generally is not possible because of the poor current carrying capacity of ITO. Similarly, electroless deposition of metals can be challenging, as the chemicals in a plating bath can undergo undesirable side reactions with the ITO, often resulting in etching of the ITO while plating. Silver ink printing on the ITO has also been used to provide the bus bar, but can be very expensive and not suitable for a fine pitch patterning.